Hydrogen produced by electrolysis is one of the promising means by which to store electricity coming from renewables and to address its intermittency. With the growing global electricity share from renewable energy sources, large-scale storage systems are required. Alkaline electrolysis can be a sustainable solution for the large-scale energy storage system. However, high overpotential and slow kinetics particularly of the oxygen evolution reaction (OER) still remains as a hurdle to limit efficiency of the system. To enhance efficiency of alkaline electrolysis cells, catalysts which have high electrocatalytic activity for OER should be developed.

 Platinum-like behavior of Tungsten carbide in surface catalysis was first reported by Levy and Boudart in 1973[1]. In addition, tungsten carbide was reported to have Pt-like electronic structure by Colton in 1975[2]. After that, tungsten carbide has been studied widely and expected to substitute noble metal catalysts which are used in many electrochemical reactions. Here, we studied tungsten carbide as a support for 3d-transition metals and make bi-metallic surfaces for developing a high activity OER catalyst.

 First, WC-Co was synthesized by heat treatment. Carbon nitride (g-C₃N₄) and tungsten chloride were used as a carbide precursor and cobalt acetate was also used for helping carbonization of tungsten. After heat treatment, acidic leaching process was followed to eliminate cobalt. Through additional mixing with Nickel precursor and heat treatment, Ni/WC was synthesized and to compare electrocatalytic activity Ni/C was also prepared. In addition, many different Ni/WC which have different Ni to WC ratios were synthesized and measured in electrochemical way. Finally, the optimal ratio was determined and it show better electrocatalytic activity than precious catalysts and any other non-noble catalysts.

 Cyclic voltammetry was measured to evaluate OER activity in 1 M KOH in potential range from 1 to 1.8 V. Figure 1 shows that pure WC and Ni/C have 394 mV and 413 mV overpotentials at 10 mA∙cm^-2 respectively. In Metal/WC cases, Cobalt/WC shows only 417 mV. But Nickel/WC shows 340 mV overpotential at 10 mA∙cm^-2 and higher electrocatalytic activity for OER than RuO₂ in alkaline media.

	η @ 10 mA cm-2 (mV)
Ni/C	394
WC	413
Co/WC	417
Ni/WC	340
RuO2	355

Table1. Activities for OER at 10 mA cm^-2

References

[1] R. B. Levy, M. Boudart, Science, New series, Vol. 181, No. 4099 (1973) 547-579

[2] Richard J. Colton, Jan-Tsyu j. Huang, J.Wayne Rabalais, Chemical Physics Letters, Vol. 34, No. 2 (1975) 337-339

Figure1. Cyclic voltammetry for the oxygen evolution reaction in 1 M KOH of Ni/C, WC, Co/WC, Ni/WC, RuO₂